Question

On a see-saw, two boys are sitting. One of them weighing 50 kg is sitting at a
distance 2 m from the middle. At what distance should another boy of 25 kg sit
from the middle so that the see-saw is balanced?​

Answer 1

Answer:

Let the two children be sitting on the left arm. They will produce anti-clockwise moment due to their weights about the middle point.

Total Anti-clockwise moment = 30 kgf x 2m + 50kgf x 2.5 m

= 60 kgf m + 125 kgf m = 185 kgf m

To balance it, the man should sit on the right arm (to produce clockwise moment). Let his distance from the middle be x m. Then

Clockwise moment = 74 kgf x X m = 74x kgf m

By the principle of moments,

Anti-clockwise moment = Clockwise moment

185 = 74x

or x = 185/74m

= 2.5 m (on the other side).